1 files changed, 60 insertions, 0 deletions

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index a3e7fb484938..2187211893ff 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -506,6 +506,57 @@ static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
 	return err;
 }
 
+static struct fuse_sync_bucket *fuse_sync_bucket_alloc(void)
+{
+	struct fuse_sync_bucket *bucket;
+
+	bucket = kzalloc(sizeof(*bucket), GFP_KERNEL | __GFP_NOFAIL);
+	if (bucket) {
+		init_waitqueue_head(&bucket->waitq);
+		/* Initial active count */
+		atomic_set(&bucket->count, 1);
+	}
+	return bucket;
+}
+
+static void fuse_sync_fs_writes(struct fuse_conn *fc)
+{
+	struct fuse_sync_bucket *bucket, *new_bucket;
+	int count;
+
+	new_bucket = fuse_sync_bucket_alloc();
+	spin_lock(&fc->lock);
+	bucket = rcu_dereference_protected(fc->curr_bucket, 1);
+	count = atomic_read(&bucket->count);
+	WARN_ON(count < 1);
+	/* No outstanding writes? */
+	if (count == 1) {
+		spin_unlock(&fc->lock);
+		kfree(new_bucket);
+		return;
+	}
+
+	/*
+	 * Completion of new bucket depends on completion of this bucket, so add
+	 * one more count.
+	 */
+	atomic_inc(&new_bucket->count);
+	rcu_assign_pointer(fc->curr_bucket, new_bucket);
+	spin_unlock(&fc->lock);
+	/*
+	 * Drop initial active count.  At this point if all writes in this and
+	 * ancestor buckets complete, the count will go to zero and this task
+	 * will be woken up.
+	 */
+	atomic_dec(&bucket->count);
+
+	wait_event(bucket->waitq, atomic_read(&bucket->count) == 0);
+
+	/* Drop temp count on descendant bucket */
+	fuse_sync_bucket_dec(new_bucket);
+	kfree_rcu(bucket, rcu);
+}
+
 static int fuse_sync_fs(struct super_block *sb, int wait)
 {
 	struct fuse_mount *fm = get_fuse_mount_super(sb);
@@ -528,6 +579,8 @@ static int fuse_sync_fs(struct super_block *sb, int wait)
 	if (!fc->sync_fs)
 		return 0;
 
+	fuse_sync_fs_writes(fc);
+
 	memset(&inarg, 0, sizeof(inarg));
 	args.in_numargs = 1;
 	args.in_args[0].size = sizeof(inarg);
@@ -763,6 +816,7 @@ void fuse_conn_put(struct fuse_conn *fc)
 {
 	if (refcount_dec_and_test(&fc->count)) {
 		struct fuse_iqueue *fiq = &fc->iq;
+		struct fuse_sync_bucket *bucket;
 
 		if (IS_ENABLED(CONFIG_FUSE_DAX))
 			fuse_dax_conn_free(fc);
@@ -770,6 +824,11 @@ void fuse_conn_put(struct fuse_conn *fc)
 			fiq->ops->release(fiq);
 		put_pid_ns(fc->pid_ns);
 		put_user_ns(fc->user_ns);
+		bucket = rcu_dereference_protected(fc->curr_bucket, 1);
+		if (bucket) {
+			WARN_ON(atomic_read(&bucket->count) != 1);
+			kfree(bucket);
+		}
 		fc->release(fc);
 	}
 }
@@ -1418,6 +1477,7 @@ int fuse_fill_super_common(struct super_block *sb, struct fuse_fs_context *ctx)
 	if (sb->s_flags & SB_MANDLOCK)
 		goto err;
 
+	rcu_assign_pointer(fc->curr_bucket, fuse_sync_bucket_alloc());
 	fuse_sb_defaults(sb);
 
 	if (ctx->is_bdev) {